FIGS. 33A-33C show an example of lancing apparatus. The lancing apparatus 90 shown in the figures includes a lancet 902 which is moved along with a lancet holder 901 by the resilient force of a coil spring 900 to lance skin. As shown in FIG. 33A, in the lancing apparatus 90, the coil spring 900 can be kept in the state for storing the resilient force by latching an engagement claw 903 of the lancet holder 901 to a stepped portion 905 of a housing 904. As shown in FIG. 33B, the latched state can be released by pushing an operation cap 906 to bring an operative portion 907 of the operation cap 906 into contact with the engagement claw 903 and disengaging the engagement claw 903. As shown in FIG. 33C, when the latched state is released, the resilient force of the coil spring 900 acts on the lancet holder 901 to move the lancet 902, along with the lancet holder 901, in a lancing direction N1. As a result, the lancet 902 sticks in skin.
Another example of lancing apparatus utilizes a cam mechanism for lancing skin with the lancet (See JP-U 64-42010 and JP Patent No. 2702374, for example).
FIGS. 34A-34C show the lancing apparatus disclosed in JP-U 64-42010. In the lancing apparatus, the rotational movement of a cam 910 is converted into reciprocal movement of a lancet supporter 911, and the lancet 92 is moved along with the lancet supporter 911 to lance the skin. Shown in FIG. 34A is a lance wait state of this lancing apparatus 91, in which the cam 910 is fixed, with the coil spring 913 storing the resilient force. From this state, by operating a rotation lever 914, the cam 910 is released from the fixed state, as shown in FIGS. 34B and 34C. As a result, the cam 910 rotates around a shaft 915. The cam 910 is formed with a V-shaped cam groove 916, with which an engagement pin 917 integrally formed on the lancet supporter 911 engages. Therefore, when the cam 910 rotates, the engagement pin 917 moves along the cam groove 916. As a result, the lancet supporter 911 moves reciprocally in the lancing direction N1 and the retreating direction N2 while being guided by a slide hole 918, whereby the lancet 912, along with the lancet supporter 911, moves reciprocally in the lancing and the retreating directions N1 and N2.
The lancing apparatus 91 further includes a mark member 919 for preventing the lancet 912 from unintentionally projecting in a non-lancing period to enhance the safety and realizing a proper lancing depth. The mark member 919 includes a slide member 919A, and a mark plate 919B which moves along with the slide member 919A. The side member 919A and the mark plate 919B are biased toward the lancing direction N1 and can be moved in the retreating direction N2 by pressing the lancing apparatus 91, with the mark plate 919B held in contact with the skin.
As shown in FIG. 35, the lancing apparatus disclosed in JP Patent No. 2702374 includes a housing 920 accommodating a transmission member 921 and a lancet holder 922. The lancet holder 922 can be moved in the lancing and the retreating directions N1 and N2 due to the rotation of the transmission member 921. The transmission member 921 is rotatable in the circumferential direction in close contact with the inner surface of the lancet holder 922 and supported by the housing 920 via a coil spring 923. The transmission member 921 is provided with a drive pin 925 for engagement with a drive cam 924 of the lancet holder 922. As shown in FIG. 36, the drive cam 924 includes a first segment 924a along which the drive pin 925 moves in moving the lancet holder 922 (See FIG. 35) in the lancing direction N1, a second segment 924b along which the dive pin 925 moves in moving the lancet holder 922 (See FIG. 35) in the retreating direction N2, and a third segment 924c along which the drive pin 925 moves in twisting the coil spring 923 (See FIG. 35) for storing the resilient force.
As shown in FIG. 35, the transmission member 921 is also connected to a sealing ring 926 provided at the front end of the housing 920. By rotating the sealing ring 926, the drive pin 925 of the transmission member 921 moves in the circumferential direction to twist the coil spring 923. The transmission member 921 can be fixed by non-illustrated fixing means, with the coil spring 923 twisted and storing the resilient force. When the operation button 927 is pressed, the transmission member 921 can be released from the fixed state.
In the lancing apparatus 90 shown in FIGS. 33A-33C, after the resilient force of the coil spring 900 is transmitted to the lancet holder 901, the lancet holder 901 moves independently from the coil spring 900. Therefore, to move the lancet holder 901 smoothly, a relatively large gap is defined between the lancet holder 901 and the housing 904 in the lancing apparatus 90. Therefore, in the lancing apparatus 90, when the lancet holder 901 is released from the latched state and moved in the lancing direction N1, the lancet holder 901 and hence the lancet 902 are liable to tremble, so that the lancet 902 is liable to shake in the lancing operation. Such shake gives the user unnecessary pain.
Further, in the lancing apparatus 90, the movement of the lancet holder 901 in the lancing direction N1 is stopped when the lancet holder 901 engages the stepped portion 908 of the housing 904. Therefore, in the lancing, the impact caused by the engagement of the lancet holder 901 with the stepped portion 908 is transmitted to the skin. Such impact not only causes pain or discomfort but also transmits vibration to the lancet 902, which further increases pain in the lancing. In addition, the impact noise upon the engagement increases the feeling of the pain, and the impact noise combined with the pain due to lancing gives greater discomfort.
In the lancing apparatus 91 shown in FIGS. 34A-34C, the movement of the lancet supporter 911 is guided by the slide hole 918, so that shake of the lancet 912 is unlikely to occur. Since the lancet supporter 911 is reciprocated by the cam mechanism, the transmission of large impact to the skin and the generation of large impact sound do not occur. However, since the lancing apparatus 91 is provided with the mark member 919 for enhancing the safety in the non-lancing period, the structure of the apparatus is complicated and disadvantageous in terms of the manufacturing cost. Further, the mark member 919 is so designed that the adjustment of the pressing force exerted to the mark member for controlling the lancing depth is performed by the user's operation. Therefore, when the exerted pressing force is too small, the lancing depth becomes too small to obtain sufficient blood. Conversely, when the exerted pressing force is too large, the lancing depth becomes too large, which may cause unnecessary pain. In this way, the adjustment of the lancing depth is difficult, and the lancing apparatus 91 is inconvenient.
In the lancing apparatuses shown in FIGS. 35 and 36, the operation button 927 is pressed to move the lancet holder 922 in the lancing direction after the sealing ring 926 is rotated. Therefore, the lancing apparatus 92 is difficult to use with one hand, and hence, is inconvenient. When the coil spring 923 is twisted in use, a load is liable to be exerted onto an end of the spring 923, which shortens the lifetime of the coil spring 923. To solve such a problem, the rigidity of the coil spring need be increased, which is disadvantageous in terms of the manufacturing cost.